1. Field of the Invention
The present invention relates in general to a connector assembly and a connecting device for a steering wheel, and more particularly to such steering-wheel connector assembly and connecting device arranged to connect, in a vibration-damping manner, a steering wheel of a vehicle to a rotary member such as a steering shaft which is supported by a stationary member such that the rotary member is rotatable to steer the vehicle.
2. Discussion of Related Art
A vehicle such as an automobile is provided with a steering system including a steering wheel and a steering shaft connected to the steering wheel. When the steering wheel is rotated to steer the vehicle, the steering shaft is rotated with the steering wheel, and a rotary motion of the steering shaft is transmitted through a gear mechanism to a link mechanism connected to axles of steerable wheels, so that the steering angle of the steerable wheels is changed according to an angle of rotation of the steering wheel and shaft.
In a steering system as described above, there is interposed an elastic joint which elastically or flexibly connect a shaft of the steering gear and the steering shaft, to reduce the amount of transmission of vibrations from the axles to the steering wheel during running of the vehicle, for thereby reducing the magnitude of the vibration applied to the steering wheel which is directly manipulated by the operator or driver of the vehicle. However, the provision of the elastic joint is not sufficient to completely protect the steering wheel from the vibration applied thereto.
In a vehicle steering system generally known in the art, the steering shaft is supported by a column tube or other stationary member fixed to the body of the vehicle, such that the steering shaft is rotatable about its axis. In this arrangement, a vibration generated during an idling operation of an engine of the vehicle while the vehicle is stopped is transmitted from the vehicle body to the steering wheel through the above-indicated stationary and the steering shaft. The mere provision of the elastic joint elastically connecting the shaft of the steering gear and the steering shaft is not enough to effectively reduce the amount of the vibration transmitted from the vehicle body to the steering wheel.
There is also known a steering system of by-wire type similar to an accelerator system or braking system of by-wire type. In the by-wire type steering system, the steering shaft is not provided, and the steering wheel is connected to a rotary member which is supported by a stationary member fixed to the vehicle body such that the steering wheel is rotatable about its axis with the rotary member. An actuator to change the angle of the steerable wheels is controlled by an electronic control device according to a rotary motion of the steering wheel. In this steering system of by-wire type, the above-indicated elastic joint elastically connected to the shaft of the steering gear and the steering shaft cannot be used for damping the vibration of the steering wheel.
In view of the above-indicated problem of the known steering system, various types of connector structure for connecting the steering wheel to the steering shaft have recently been proposed in an attempt to minimize the amount of vibration transmitted from the vehicle body to the steering wheel.
One of the various types of connector structure includes a dynamic damper provided at a central boss portion of the steering wheel, as disclosed in JP-A-5-238394 and JP-A-2001-239943. The dynamic damper includes a spring portion in the form of an elastic body and a mass portion, and the steering wheel is connected to the steering shaft, at the central boss portion provided with the dynamic damper. In this type of connector structure, the vibration of the steering wheel is effectively damped owing to resonance of the dynamic damper. However, the steering wheel provided with the dynamic damper tends to be considerably complicated in construction.
JP-A-9-71208 discloses another type of connector structure, which includes an elastic member interposed between the steering wheel and a plate fixed to the steering shaft. The steering wheel and the plate are fixed together with suitable fastening means such as bolts, with the elastic member interposed therebetween. In this simple arrangement of steering-wheel connector structure, the amount of the vibration transmitted from the steering shaft to the steering wheel is reduced owing to elastic deformation of the elastic member interposed at the connection between the steering shaft and the steering wheel.
In the known steering-wheel connector structure described just above, the amount of elastic deformation of the elastic member is limited since the steering wheel is fixed or connected to the steering column by suitable fastening means such as screws. Accordingly, the elastic member does not provide a sufficient or satisfactory damping effect based on the elastic deformation, with respect to the vibration of the steering wheel.
To permit a sufficient amount of elastic deformation of an elastic body interposed between the steering wheel and the steering shaft, it is considered to eliminate the screws or any other fastening means used to fix the steering wheel to the steering shaft, so that the steering wheel and the steering shaft are connected to each other by only the elastic body. In this case where the steering wheel and the steering shaft connected together by only the elastic body, the elastic body is permitted to exhibit a considerably low degree of torsional spring stiffness, undesirably resulting in an accordingly low rate of transmission of a rotary motion of the steering wheel to the steerable wheels, namely, an accordingly low degree of response of the steering wheels to the rotary motion of the steering wheel, as felt by the vehicle operator, and a low degree of maneuverability of the steering wheel.